MMPC-UCD MICROBIOME RESEARCH AND DEVELOPMENT PROJECT ABSTRACT (RESEARCH PROJECT) Bariatric surgeries, such as Roux-en-Y gastric bypass (RYGB), achieve rapid improvements in glucose homeostasis and long-term maintenance of reduced body weight. Obesity in humans and rodent models is associated with changes in the gut microbiota and bariatric surgery produces significant changes in the gut microbiota in obese humans; after RYGB the gut microbiota more closely resembles that of lean individuals. Similar changes are seen in rodent models of bariatric surgery; both RYGB and vertical sleeve gastrectomy (VSG) produce significant changes in the gut microbiota. The diversity of the gut microbiota and abundance at phyla and genera level differ in the different regions of the GI tract in rodent diet-induced obesity. How these changes in the microbiota in the different gut regions contribute to body weight gain or insulin resistance, or how these are modified after bariatric surgery is not known. The overarching goal of this study is to determine how the gut microbiota contributes to the physiological improvements seen with RYGB. A further goal of this proposal is to establish the pipeline to measure, analyze and integrate data from metabolomics and transcriptomics with the microbial community taxonomic profiles using bioinformatics tools and multivariate modeling. This project will utilize the expertise, resources, and services of all 4 Cores in our MMPC-UCD: Animal Care (Core B) and the 3 Phenotyping Cores (C, D, and E). Further, the metabolomic and functional characterization of the microbiota and host as well as the integrative analyses will be made available as Core services to clients of our Center. In Specific Aim I, the temporal and regional microbiota, host and microbial transcriptome, and metabolome of the intestinal tract after RYGB surgery will be determined. The hypothesis to be tested is that the gene expression and metabolism of the microbiota after RYGB induce changes in energy balance in the host that result in maintenance of weight loss and improved glucose homeostasis. Using a multi- omic (metagenomic, transcriptomic, and metabolomic) approach, the microbial community and metabolome of the luminal microbiota in the small and large intestine during both the active weight loss phase and stable weight maintenance phase after sham or RYGB surgery in male and female mice will be determined. The transcriptional responses of the gut and microbial population will be characterized, and data used to identify important biological pathways involved in the beneficial response to RYGB surgery. Specific Aim II will determine whether transplantation of RYGB microbiota protects mice from the deleterious effects of a HFD. The hypothesis to be tested is that that the RYGB microbiota regulates host physiology through production of metabolites and altered host-microbe crosstalk to decrease body weight and adiposity, and improve metabolic status. Contents from different regions of the gut from sham or RYGB mice will be used to colonize male and female germ-free mice subsequently challenged with low-fat diet (LFD) or HFD. The multi-omic approach developed in Specific Aim I will be used to identify microbial populations, and to characterize the transcriptional responses and metabolites of the gut, luminal contents, liver and skeletal muscle. We anticipate that we will identify a number of metabolites and a transcriptional signature that distinguishes RYGB microbiota recipients from sham recipients and that changes in metabolites and transcription are involved in the mechanisms bestowing protection from the negative effects of a HFD.